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Land Use, Land Use Change and Forestry (LULUCF) contributed 24% of total greenhouse gas emissions and 11% of CO2 emissions in the 2000-2009 period (IPCC, 2014). Land-based mitigation strategies are essential to achieve the 2oC target, with most current scenario projections invoking substantial negative emissions from afforestation and from bioenergy with carbon capture and storage (BECCS), in addition to Reduced Emissions from Deforestation and Degradation (REDD+) and improved agricultural management. Reporting and accounting of some LULUCF activity is already embedded in international climate policy. Negotiations leading up to adoption of new international policies at the Paris 2015 Climate Summit include further LULUCF activities, particularly REDD+. This reliance on land-based mitigation options necessitates that LULUCF policy is in-line with the latest evidence across the natural, economic and social sciences, and that scientific research reflects policy needs. This presentation will review the importance of LULUCF mitigation options in current and planned policy, indicating mismatches with scientific knowledge, often due to different considerations of spatial and temporal scales. We will also explore time lags between the emerging scientific insights, policy targets and commitments and changes in activity leading to desired changes in physical and ecological systems.

For example, scientific research has long emphasised the importance of REDD+ as a low cost, multiple-benefit near-term mitigation option, although international policy is only just catching up. New analyses of the biophysical climate impacts of land use change from both observations and Earth System Modelling (ESM) further confirm the importance of tropical forests as providing a cooling effect through changes in the surface energy budget and in evapotranspiration rates. The biophysical climate effects of afforestation in temperate and boreal areas can however either amplify the biogeochemical cooling effects (e.g through enhanced evapotranspiration in summer) or dampen them (e.g. through reduced surface albedo in winter). At the global scale, net biophysical effects are small and biogeochemical effects of land sources and sinks of CO2 dominate the climate impacts of LULUCF. The regional nature of the effects and the still large uncertainty in the science imply that the evidence base is not yet sufficient to implicate changes in international mitigation policy, particularly related to afforestation/reforestation activities, although effects are likely be important to consider in regional or national adaptation policy. Biophysical effects should be considered in the current development of land-based mitigation scenarios and modelling capability for the next generation of integrated climate-nature-society-policy projections so the implications can be assessed.

Bioenergy has been one sector where controversies in scientific understanding, socio-economic modelling and policy implementation have been particularly apparent and there is a need for the stronger use of evidence and more joined up approach. Recent studies suggest that in the longer term bioenergy may provide larger offsetting potential than afforestation where contribution is small once forests reach maturity. However, to fully reach the potential it will be important to ensure technological improvements, assessment of full life-cycle costs, and the implementation of sustainability criteria. Given the potential lags in the scientific, technological and uptake steps, more resources needs to be put in place now or soon if BECCS is to be expected to contribute significantly to global mitigation by 2050.

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The objectives of the LUCID international project are to qualify and quantify robust biogeophysical and biogeochemical impacts of land-use induced land-cover changes on climate (LULCC), from pre-industrial times to nowadays, and from today till the end of the 21st century. By ‘robust’ we mean that is above the noise generated by model variability and consistent across multiple climate models.

Two steps were undertaken for the 1st phase: one focused on historical climate (from ~1870 till years 2000), and another looking into the future (outlook and papers may be found on our web site: http://www.lucidproject.org.au/index.html).

Seven modelling groups contributed to the historical part. They all conducted two series of two experiments using observed interannually and seasonally varying SST and sea ice extent for both present-day and pre-industrial conditions, forced with two sets of land cover distributions reflecting the state of the canopy respectively in ~1870, and ~1992.

We have demonstrated that climate change in large regions of the northern hemisphere may be as much influenced by LULCC than by changes in global quantities (CO2, SSTs, …), with either amplifying or dampening effects. Moreover extremes (e.g. temperature) simulated in climate models are quite sensitive to LULCC (Pitman et al. 2012). Detection/attribution of local to regional changes in climate/meteorology may therefore be strongly biased if one does not account for changes in local to regional land-uses. Similarly we emphasized that downscaling of global climate simulations must include land-cover (and/or land-use) changes.

We have also shown that the response of individual models to deforestation varies not only in magnitude but also in sign from one model to another for some variables such as latent heat flux. This diversity could certainly be better constrained by a proper evaluation of our land-surface models (or DGVMs) in both an off-line and on-line mode. There is a need to properly evaluate the sensitivity of our LSMs (and then our coupled LSM-GCMs) to land cover changes and to land uses using a wide range of observations as for example was done in Boisier et al. (2013 and 2014).

During the LUCID exercise, we have discovered that going from a set of crops and pasture maps to land-cover maps was not only a difficult task as it involves choices, but was also a mean to increase the dispersion between the models’ results. There is therefore a need to harmonize the procedure to go from those maps to land-cover. This is highly important for the biogeophysical effect on climate, and is crucial for the carbon cycle. Moreover, as DGVMs become more complex and start to include better representation of crop function and management, we’ll soon be facing the need to better interact upstream IAMs who provide climate modelers with such maps.

The LUCID community also contributed to the fifth Coupled Model Intercomparison Project (CMIP5) and analyzed scenarios of future climate change. Six CMIP5 modeling groups performed additional LUCID-CMIP5 simulations without anthropogenic land-use changes from 2006 to 2100. Those analyses revealed that the effects of land-use changes on mean annual temperature in RCP8.5 and 2.6 scenarios are significant for regions with land-use changes exceeding 10%. Changes in land-surface albedo, available energy, and latent heat fluxes are small but significant for most ESMs in regions affected by land-use change (Brovkin et al., 2013). These climatic effects are relatively small, as land-use changes in the RCP2.6 and RCP8.5 scenarios are small in magnitude and mainly limited to tropical and subtropical regions. Crops tend to warm climate in most areas and models. A causal link between LULCC forcing and the climate impact is found in some models where the presence of pastures tends to induce a local biogeophysical cooling which offsets a biogeochemical warming. Conversion to pastures thus may have a climate change mitigation potential but more detailed and idealized experiments are required.

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Shared Socio-economic Pathways – a framework for assessing potential land use futures –

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This contribution is an invited keynote aimed at the session "Global scenarios of land-use change and land-based mitigation, and their importance in the climate system” - please exclude this paragraph from the final abstract -

Today, land-use and land-use change are responsible for approximately a quarter of global greenhouse gas emissions, largely from tropical deforestation, methane emissions from livestock and rice cultivation, and nitrous oxide emissions from livestock and fertilized soils. But, the land system is also seen to contribute much to climate change mitigation in the future by providing biomass for bioenergy, improved agricultural management and conserving or even enhancing carbon stocks of ecosystems. The degree of both, future emissions but also mitigation potential of the land depend strongly on uncertain trends in population growth, dietary changes, trade, possible demand for non-food products such as bioenergy, future developments in agricultural yields and relevant policies. Over time, these uncertainties may result in very different land-use patterns and associated emissions.

Scenario analysis has been established as a tool to explore and evaluate such extensive uncertainties associated with possible future developments. Recently, new scenarios have been developed that are organized around two important dimensions: The five radiative forcing levels consist of four representative concentration pathways (RCPs) which determines the amount of climate change. The possible future socio-economic conditions that could correspond to individual forcing levels are then described in the shared socio-economic pathways (SSPs). The SSPs provide 5 different stories of future socio-economic development, including possible trends in agriculture and land use. Future emissions and carbon stock dynamics in the land system are a function of complex interaction between all kinds of socio-economic factors, including population dynamics, economic development, technological change, trade, cultural and institutional changes and interaction with other sectors such as bioenergy demand for energy supply and transport. In each of the SSPs, climate policies can be introduced to reduce emissions or to enhance carbon uptake to reach radiative forcing level targets consistent with the RCP scenarios.

In this presentation, we will first present relevant aspects of the SSP framework for the land system. Then, based on a study that applied the scenario matrix approach combining climate forcing and socioeconomic dimensions for so-called integrated assessment models (IAMs) with dedicated land use modules, we will focus on possible future pathways for these drivers and their consequences on the land system, associated emissions and mitigation potential.

Risk-aversion Behavior in Smallholder Farmers and Climate Change. Evidence from Empirical Work in Zambia

A. De Pinto (International Food Policy Research Institute, Washington, DC, United States of America), V. Smith, (Montana State University, Bozeman, United States of America), R. Robertson, (International Food Policy Research Institute, Washington, DC, United States of America), A. Haruna, (International Food Policy Research Institute, Washington, DC, United States of America)

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Risk-aversion Behavior in Smallholder Farmers and Climate Change. Evidence from Empirical Work in Zambia

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When the economic effects of climate change are considered, decision-making under uncertainty and risk are arguably at the forefront of the problems that need to be analyzed. The consensus is that, in the developing world, smallholder farmers are among the most vulnerable to the effects of climate change and, especially, to the adverse consequences that derive from more volatile and extreme weather events with which climate change is associated. Further, there is overwhelming empirical evidence that risk considerations affect farmers’ land allocation and other input usage decisions as well as their technology adoption choices. However, apart from the body of research on index insurance, an extensive review of the empirical literature that deals with climate change reveals that uncertainty and the role of risk-aversion are notably not taken into account in models that estimate the impacts of climate change on agricultural production, market prices and food security for the poor. In particular, those models do not consider the effects of climate change related increases in yield and price volatility on farm household choices with respect to production strategies that provide adaptation or mitigation services. In fact, farmers and farm households respond to changes in the riskiness of their decision making environments as well as to changes in expected average yields, crop prices and input prices. How they respond depends on many factors, but attitudes to risk are widely viewed as important in many contexts, not least when exogenous shocks such as climate change alter the fundamental nature of the production environment in which farmers operate. We therefore explore the role of risk in the farm household’s production decisions by using a widely available household survey of farmers in Zambia to build a theoretically based empirical model of land-use choices. The model accounts for attitudes to risk in analyzing the effects of climate change on farm-level land allocation to crop production. The empirical specification is based on a relatively simple discrete-choice model (nested logit) augmented by risk variables consistent with a mean-variance utility function. After the system is shocked with changes in temperatures, precipitation, and distribution of crop yields consistent with regional effects of climate change, the household decisions and the resulting production trends are aggregated and evaluated at the country level. Shifts in the geographical pattern of crop production appear evident using this analysis with crops like millet and cassava largely replacing maize production. More importantly, results indicate that in the case of Zambia the aggregate effects of risk-mitigating decisions exacerbate trends driven by the biophysical changes caused by climate change. These decisions represent a form of adaptation of small households to the changing climate. The effects of this form of adaptation, developed in the constraints of smallholder production, appear to be detrimental for the total output from the agricultural sector with important implications for market prices and food security for both the rural and urban poor. Three important conclusions follow from our analysis. First, risk matters; its effects on farmers’ production decisions should not be ignored and should be accounted for in empirical models of the impacts of climate change. Second, concentrating on farm-level responses to climate change is not sufficient. It is essential to develop methods of aggregating individual responses to climate-change-related shifts in risk so that they can be reflected in models of regional and national crop and livestock markets. This is required to better understand the implications of climate change for ecosystem services and food and income security. Third, our results suggest that not accounting for farmers’ risk attitudes can lead to significant mistakes in policy planning. It is also the case that a more accurate estimate of the effects of climate change on farmers’ land-use and production decisions will enable policy makers to more accurately assess the benefits and costs of a wide range of policies intended to mitigate climate change’s adverse effects.

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This contribution is aimed at the session "Global scenarios of land-use change and land-based mitigation, and their importance in the climate system” - conveners Arneth/Stehfest/Popp.

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Future impacts of land-use and land-cover changes (LULCC) on the biochemical cycles and biophysics are highly uncertain. Firstly, there are large uncertainties in possible future scenarios due to socio-economic parameters (e.g., food demand, trade liberalisation, technological development). Secondly, there are uncertainties in how cropland, pasture and natural vegetation respond to changes in climate. With a model comparison we address both these uncertainties. Three different future scenarios are run with the Integrated Assessment Models (IAMs) IMAGE and MAgPIE. The socio-economic setting in all scenarios is based on the Shared Socioeconomic Pathways 2 (SSP2), and all scenarios include climate change impacts for RCP2.6, which have direct effects on crop yields and terrestrial carbon stocks, and indirect effects on land-use dynamics. A bio-energy with carbon capture and storage scenario (BECCS) and an afforestation and avoidance of deforestation scenario (AD+AFF) are compared to a reference scenario with no land-based mitigation (REF). The land use changes from these 6 IAM scenarios are subsequently used to run the 4 Dynamic Global Vegetation Models (DGVMs) JULES, LPJ-GUESS, LPJml and ORCHIDEE. This comparison will show the impact of different future mitigation scenarios on the carbon and water balance, the development of natural vegetation and crop yields over the 21st century.

Understanding the role of land management for carbon and climate mitigation under RCP 4.5 and RCP 8.5 using the Community Earth System Model

P. Lawrence (National Center for Atmospheric Research, Boulder, United States of America), B. O'neill (National Center for Atmospheric Research (NCAR), Boulder, CO, United States of America)

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Understanding the role of land management for carbon and climate mitigation under RCP 4.5 and RCP 8.5 using the Community Earth System Model

P. Lawrence (1) ; B. O'neill (2) (1) National Center for Atmospheric Research, Climate and Global Dynamics Division, Boulder, United States of America; (2) National Center for Atmospheric Research (NCAR), Boulder, CO, United States of America

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As part of the Coupled Model Intercomparison Project phase 5 (CMIP5), land cover change and wood harvest were prescribed as major climate forcings for historical and future Representative Concentration Pathway (RCP) projections. Lawrence et al. (2012) described how land cover change was prescribed in all of these simulations and how the climate system and carbon cycle responded to the land cover change in concert to other transient forcing in the Community Earth System Model (CESM). The attribution of carbon cycle and climate changes directly due to land cover change however, were not possible due to the design of the CMIP5 experiments. Through a series of new CESM simulations we have attributed the land cover change impacts for the historical time series as well as RCP 4.5 and RCP 8.5 with and without land cover change. These simulations show that the direct land cover change fluxes to the atmosphere found in the CMIP5 simulations did not account for the lost uptake of carbon that would have been possible in the absence of land cover change and wood harvest. Once these losses are taken into account, the historical losses of terrestrial carbon increased from 61.2 PgC to 129.6 PgC, the RCP 4.5 uptake of 62.8 PgC changed to a loss of 5.8 PgC, and the RCP 8.5 loss of 49.0 PgC increased to 168.8 PgC. In order to assess the potential of land management to mitigate carbon and climate consequences we are currently simulating RCP 4.5 and RCP 8.5 with large scale global afforestation scenarios compared to maximum biofuel production through increased crop lands. In this talk we present the differences in all of these experiments for both ecosystem carbon and climate. To conclude this presentation we will provide details on the proposed land use simulations for CMIP6, currently being designed in the Land Use Model Intercomparison Project (LUMIP).